Update PR template to ask for release type (Azure#23528)

* Update PULL_REQUEST_TEMPLATE.md

* Update PULL_REQUEST_TEMPLATE.md

* Update repo question

* Update PULL_REQUEST_TEMPLATE.md

* Update CONTRIBUTING.md

.github/PULL_REQUEST_TEMPLATE.md

@@ -6,20 +6,15 @@
 
 ## Checklist
 
+- **Mandatory**: please state whether this PR targets a [**general** release](../blob/main/CONTRIBUTING.md#target-release-types) / [**public preview**](../blob/main/CONTRIBUTING.md#target-release-types) / [**private preview**]((../blob/main/CONTRIBUTING.md#target-release-types)) / [**engineering build**](../blob/main/CONTRIBUTING.md#target-release-types) of Azure PowerShell?
+    - `{Enter your answer here}`
 - [ ] Check this box to confirm: **I have read the [_Submitting Changes_](../blob/main/CONTRIBUTING.md#submitting-changes) section of [`CONTRIBUTING.md`](../blob/main/CONTRIBUTING.md) and reviewed the following information:**
 
-* **SHOULD** select appropriate branch. Cmdlets from Autorest.PowerShell should go to [`generation`](https://github.com/Azure/azure-powershell/tree/generation) branch. 
-* **SHOULD** make the title of PR clear and informative, and in the present imperative tense. 
 * **SHOULD** update `ChangeLog.md` file(s) appropriately
-    * For any service, the `ChangeLog.md` file can be found at `src/{{SERVICE}}/{{SERVICE}}/ChangeLog.md`
-    * A snippet outlining the change(s) made in the PR should be written under the `## Upcoming Release` header in the past tense. Add changelog in description section if PR goes into [`generation`](https://github.com/Azure/azure-powershell/tree/generation) branch.
+    * For SDK-based development mode, update `src/{{SERVICE}}/{{SERVICE}}/ChangeLog.md`.
+        * A snippet outlining the change(s) made in the PR should be written under the `## Upcoming Release` header in the past tense. 
+    * For autorest-based development mode, include the changelog in the PR description.
     * Should **not** change `ChangeLog.md` if no new release is required, such as fixing test case only.
-* **SHOULD** have approved design review for the changes in [this repository](https://github.com/Azure/azure-powershell-cmdlet-review-pr) ([_Microsoft internal only_](../blob/main/CONTRIBUTING.md#onboarding)) with following situations
-    * Create new module from scratch
-    * Create new resource types which are not easy to conform to [Azure PowerShell Design Guidelines](../blob/main/documentation/development-docs/design-guidelines)
-    * Create new resource type which name doesn't use module name as prefix
-    * Have design question before implementation
 * **SHOULD** regenerate markdown help files if there is cmdlet API change. [Instruction](../blob/main/documentation/development-docs/help-generation.md#updating-all-markdown-files-in-a-module)
 * **SHOULD** have proper test coverage for changes in pull request.
-* **SHOULD NOT** introduce [breaking changes](../blob/main/documentation/breaking-changes/breaking-changes-definition.md) in Az minor release except preview version.
 * **SHOULD NOT** adjust version of module manually in pull request

CONTRIBUTING.md

@@ -90,6 +90,27 @@ completed checklist.
 The following set of guidelines must be adhered to when opening pull requests in the Azure
 PowerShell repository.
 
+#### Target Release Types
+
+Here are all types of releases of **Azure PowerShell**. Note that the type of release isn't necessarily aligned to the state of the swagger or service feature.
+
+- **General** release
+  - This PR targets an [official general release](https://github.com/Azure/azure-powershell/milestones) of Azure PowerShell.
+  - Target version is `x.y.z`, no suffix.
+    - Note: versions < 1.0.0 are also included in this category.
+  - Target branch should be `main` or `generation` depending on the development approach.
+- **Preview** release
+  - **Public preview**
+    - This PR targets a preview release of Azure PowerShell. It is independent to the normal release cycle.
+    - Target version is `x.y.z-preview`.
+      - Note: if the major version is 0, it is considered a general release rather than preview.
+    - Target branch should not be `main` nor `generation`. Please contact [sprint master](https://github.com/Azure/azure-powershell/milestones) if you are unsure about which branch to target.
+  - **Private preview** / **Embargoed preview**
+    - This PR is related to some business secret. It should not be submitted to this repository. Contact [sprint master](https://github.com/Azure/azure-powershell/milestones) for more details.
+- **Engineering build**
+  - This PR does not require any kind of releases. It's for internal or private distribution.
+  - Target branch should not be `main` nor `generation`. Please contact [sprint master](https://github.com/Azure/azure-powershell/milestones) if you are unsure about which branch to target.
+
 #### General guidelines
 
 The following guidelines must be followed for **every** pull request that is opened.